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A 26-year-old woman who is 27 weeks pregnant presents in labour. She is febrile and describes a mild ’flu-like illness with aches and pains for 24 hours. Urine dipstick is negative for blood and nitrates. She has no localizing signs.
1. What bacterial infections are you concerned about?
Any form of sepsis can precipitate premature labour because of the cytokine response it induces. Pyelonephritis is less likely in this case because of the negative urine test but should be considered. Other possibilities include group B haemolytic streptococcus and listeria.
2. The baby is born with hepatosplenomegaly, thrombocytopenia and pneumonitis. What are the commonest causes of neonatal sepsis?
Group B streptococcus, listeria and E. coli are all causes of neonatal sepsis. In this case the maternal history of a mild illness combined with premature labour and neonatal sepsis point towards listeriosis.
3. How will you identify listeria in the laboratory?
Listeria is a Gram-positive bacillus that has a narrow zone of haemolysis and is motile at room temperature. Further speciation is by a range of biochemical tests.
4. How is listeria acquired?
Listeria are carried in the gut of many animals. Acquisition is from the consumption of contaminated food stuffs. This is particularly likely with unpasteurised ripe cheeses, refrigerated salads such as coleslaw, ready-meals and pre-prepared refrigerated meals.
5. How can listeria infection be prevented?
The key to this is the ability of listeria to grow at 4 °C. Pregnant women and immunocompromised patients should avoid high-risk foods. Food should be stored below 4 °C in food production and storage areas and should be consumed within 4 days. Steps to reduce contamination of ready-to-eat food by uncooked food should also be taken.
6. What other ways does this infection present?
The spectrum of listeria infection ranges from being asymptomatic through a mild ’flu-like illness to fulminant septicaemia and meningo-encephalitis. Severe disease is more likely in patients with diminished cell-mediated immunity.